This invention broadly relates to immunochemical assays and more particularly to radioimmunoassays (RIAs) for the detection and determination of cortisol in a biological sample.
The ability to evaluate the presence of cortisol, an adrenocortisol steroid, is of particular interest to clinicians and researchers alike because of its important role in adrenal cortex functions. It is readily appreciated that an accurate assay for such a physiological component would be extremely valuable in the diagnosis and treatment of a variety of adrenal metabolic disorders.
In radioimmunoassay or competitive protein binding radioassays, the compound to be measured, usually an antigen, is allowed to compete with a similar or chemically related radioactive compound for binding sites on an antibody or on a specific binding protein. Measuring the amount of bound labeled antigen in the standard antibody solution will indicate the amount of targeted compound present in the sample.
Ideally, the antibodies employed should be so specific that they will bind only with the compound or class of compounds to be detected. Often biological fluids contain substances very closely related to the target compound and it is not unusual for antibodies to be unable to distinguish the target compound from closely related metabolites or its congeners.
Just as it is necessary for the antibody to exhibit a high degree of specificity for the target compound, it is important that the antibody exhibit equal affinity for the detectably-labeled compound. Thus, it would be extremely beneficial to prepare a labeled derivative of the target compound which would be indistinguishable from and compete with the target compound for binding sites on the antibody.
Accordingly, it is an object of the invention to provide a method for the synthesis, purification and resolution of stereoisomeric cortisol derivatives.
It is a further object of this invention to provide a method for labeling two stereo-configurationally different cortisol-21-acetate tyrosine methyl esters.
It is an additional object of this invention to provide a reagent useful in immunochemical methods for detecting and determining cortisol in biological samples.
It is the ultimate object of this invention to demonstrate the greater sensitivity and specificity of antibodies for the syn isomer of cortisol-21-acetate tyrosine methyl ester.